Lubricating oil for diesel engines



Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE Standard Oil Development Company,

ration of Delaware a COI'PO- No Drawing. Application December 23, 1937, Serial No. 181,314

12 Claims.

This invention relates to lubricating oils for Diesel engines and is more particularly concerned with certain addition agents which when added to non-waxy lubricating oils greatly improve their properties.

It is known that certain metallic soaps, such as aluminum stearate and aluminum naphthenate improve the properties of lubricating oils for Diesel engines particularly with respect to decreasing ring sticking and varnish forming tendencies as well as increasing oiliness. A serious objection to the use of aluminum stearate for this purpose is that it tends to settle out or gel upon standing. An objection to the use of aluminum naphthenate is that it requires a temperature of 300 to 400 F. for solution in oil, and at these temperatures color deterioration is inevitable and unavoidable.

It is desirable to use a metallic soap which has all of the desirable properties of these aluminum soaps but which does not settle out on standing and does not require temperatures for solution high enough to cause color deterioration.

It has now been found that metallic soaps of acids obtained by the oxidation of sweater oil form extremely stable solutions in non-waxy lubricating oils and can be completely dissolved in amounts of 0.1 to 3% in lubricating oil at temperatures between and 200 F. at which no color deterioration occurs. The nature of these soaps and the method of preparing them will be fully understood from the following description:

In dewaxing an oil containing pressable wax, the wax precipitated in the process is called crude slack wax. This contains varying quantities of oil which is carried down with the wax. The crude slack wax is warmed to sweat out the oil. The sweated wax is called crude scale wax, and the oil obtained is called foots oil. The crude scale wax is subjected to another sweating operation and the oil so obtained is called sweater oil. It is this sweater oil obtained from the sweating of crude scale wax which is used as the starting material for the preparation of the acids desired in the present process.

Sweater oil is distinguished from crude scale wax by the fact that it contains relatively much larger quantities of oil.

the, oily layer. The aqueous layer contains the 1 sodium soaps of the desired acids along with a small amount of unsaponifiable materials. The unsaponifiable materials are then removed either by naphtha extraction or by vaporization. Sulfuric acid is added to the sodium soaps to liber- 15 ate the acids. The acids are then washed and distilled, and either a fraction of the distillate or the entire distillate and bottoms may be used for preparing the desired metallic soaps.

In preparing aluminum soaps from the acids, 20

the alkali (sodium, for example) soap is first prepared. The alkali soap solution is then added to an aluminum sulfate solution, a slight excess of the latter being used. It will be understood that if other metallic soaps are desired, appro- 25 priate solutions of the metal salts will be used or the soaps may be prepared by direct cooking of the acids with appropriate metallic oxides or hydroxides.

The aluminum soap is washed free of inorganic salts and may then be dried or may be incorporated directly in the oil without drying, in which latter case the moisture is removed from the compounded oil by blowing with air or 35 an inert gas.

The metallic soap is added to the oil in amounts of 0.1 to 3%. The oil is heated to a temperature between about 175 and 200 F. and the soap stirred into it...

Various other metals besides aluminum may 40 be used, such as calcium, nickel, cobalt, magnesium, manganese, chromium, tin, zinc, etc. These soaps may be prepared as indicated above by adding the sodium soap to a solution of the metallic salt. Other methods of preparation are, of course, not precluded.

In preparing the soap, the entire acid fraction may be used or only a portion thereof. It is found that the No. 6 cut obtained by vacuum M and steam distillation at 4 mm. of mercury and boiling between about 150 and 280 C. is particularly suitable. This fraction constitutes from to of the entire acid product.

The acid numbers and saponification numbers of the total acid and No. 6 cut respectively are approximately as follows:

Saponiil- Acid cation number Crude acid product 161 238 No. 6 out 175 239 It is found that the soaps prepared from sweater oil acids are markedly different in properties from those prepared from oxidized scale wax. For example, the acid and saponification numbers compare as follows:

Saponifl- Acid cation number No. 6 cut of oxidized scale wax; 206 230 No. 6 cut of oxidized sweater oil 175 240 It is also found that the soaps of the No. 6 cut of oxidized scale wax as such are substantially insoluble in mineral oils whereas the soap of the No. 6 cut of sweater oil acids are relatively much more soluble.

The following example illustrates the use of the improved soap:

This oil was tested for 250 hours operation on a Caterpillar Diesel engine and showed superior performance over blends of aluminium naphthenate or the aluminum soap of acids derived from the oxidation of crude scale wax in the same oil;

In someinstances, e. g. in the case of the calcium, magnesium, zinc, manganese and similar soaps, difiiculties may be encountered in dissolving them in certain mineral lubricating oils. In such cases, it has been found advantageous to add a solubilizing agent (about 5-100% or more of the weight of the soap added) to prevent gel formation and to overcome other efiects of deficiency in solubility of the soaps. Such solubilizers may be higher free fatty acids, fatty esters, naphthenic acids or esters, aromatic fatty acids such as phenyl stearic acid or their esters, organic esters of inorganic acids or aromatic polybasic acids, high molecular weight alcohols, alcoholesters, alcohol-ethers, ether-esters, and other similar high boiling compounds.

It will be understood that other addition agents besides the aluminum soaps may be added to the Diesel oils, such as oiliness agents, corrosion inhibitors, oxidation inhibitors, extreme pressure agents, thickeners, dyes, etc.

The use of these soaps is not restricted to any particular type of non-waxy lubricating oil but is app ica l g e y to all Diesel lubricati g valent metal soap of acids fractions whether obtained by the distillation, cracking, hydrogenation, destructive hydrogenation or other treatment of petroleum, coals, tars, shales, lignites or fractions thereo This invention is not limited by any theories of the mechanism of the reactions nor by any details which have been given merely for purposes of illustration, but is limited only in and by the following claims in which it is intended to claim all novelty inherent in the invention.

I claim:'

1. An improved lubricating oil composition for internal combustion engines comprising a lubricating oil containing a small amount of polyvalent metal soap of acids derived from the oxidation of sweater oil.

2. An improved lubricating oil for Diesel engines comprising a non-waxy lubricating fraction containing from 0.1 to 3% of a polyvalent metal soap of acids derived from the oxidation of sweater oil. e

3. An improved lubricating oil for Diesel engines comprising a' non-waxy lubricating fraction of petroleum containing 0.1 to 3% of a polydation of sweater oil.

4. Lubricating oil according to claim 3 in which the soap is prepared from a metal selected from the class consisting of aluminum, calcium, nickel, tin and magnesium.

5. An improved lubricating oil for Diesel engines comprising a non-waxy lubricating oil containing 0.1 to 3% of an aluminum soap of acids derived from the'oxidation of sweater oil.

6. An improved lubricating oil for Diesel engines comprising a non-waxy lubricating oil containing 0.1 to 3% of an aluminum soap of an acid fraction boiling between 150 and 280 C. at 4 mm. of mercury with steam obtained from the products of oxidation of sweater oil.

7. An improved lubricating oil composition according to claim .1 in which the soap is oil soluble.

8. An improved lubricating oil composition for internal combustion engines comprising a lubricating oil containing a small amout of a polyvalent metal soap of acids derived from the oxidation of sweater oils, the solubility of said metal soap being increased by the addition of an organic solubilizer.

9. A composition according to claim 8 in which the organic solubilizer is a higher fatty acid.

10. A composition according to claim 8 in which the solubilizer is a higher alcohol. 7

11. A method of making an improved'lubricating oil composition especially adapted for lubrication of Diesel engines, which comprises oxidizing a sweater oil fraction of pertoleum hypare acid derivatives thereof, recovering the acids from said reaction product, converting them into corresponding aluminum soaps, and incorporating 0.1 to 3% of said aluminum soap into a nonwaxy lubricating fraction of petroleum.

E R V- MUR HREE.

derived from the oxi- 

